Abstract
Sap flux density in branches, leaf transpiration, stomatal conductance and leaf water potentials were measured in 16-year-old Quercus suber L. trees growing in a plantation in southern Portugal to understand how evergreen Mediterranean trees regulate water loss during summer drought. Leaf specific hydraulic conductance and leaf gas exchange were monitored during the progressive summer drought to establish how changes along the hydraulic pathway influence shoot responses. As soil water became limiting, leaf water potential, stomatal conductance and leaf transpiration declined significantly. Predawn leaf water potential reflected soil water potential measured at 1-m depth in the rhizospheres of most trees. The lowest predawn leaf water potential recorded during this period was -1.8 MPa. Mean maximum stomatal conductance declined from 300 to 50 mmol m(-2) s(-1), reducing transpiration from 6 to 2 mmol m(-2) s(-1). Changes in leaf gas exchange were attributed to reduced soil water availability, increased resistances along the hydraulic pathway and, hence, reduced leaf water supply. There was a strong coupling between changes in soil water content and stomatal conductance as well as between stomatal conductance and leaf specific hydraulic conductance. Despite significant seasonal differences among trees in predawn leaf water potential, stomatal conductance, leaf transpiration and leaf specific hydraulic conductance, there were no differences in midday leaf water potentials. The strong regulation of changes in leaf water potential in Q. suber both diurnally and seasonally is achieved through stomatal closure, which is sensitive to changes in both liquid and vapor phase conductance. This sensitivity allows for optimization of carbon and water resource use without compromising the root-shoot hydraulic link.
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Claims 8
Claim · model-written summary
As soil water became limiting, leaf water potential, stomatal conductance and leaf transpiration declined significantly in Quercus suber.
- Taxon
- Quercus suber
Quercus subere0 - Treatment
- soil water became limitinge1
- Outcome
- leaf water potential, stomatal conductance and leaf transpiratione1
- Direction
- declinede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sap flux density in branches, leaf transpiration, stomatal conductance and leaf water potentials were measured in 16-year-old Quercus suber L. trees growing in a plantation in southern Portugal”
e1“As soil water became limiting, leaf water potential, stomatal conductance and leaf transpiration declined significantly”
Claim · model-written summary
Predawn leaf water potential of Quercus suber reflected soil water potential at 1-m depth in most trees.
- Taxon
- Quercus suberQuercus subere0
- Outcome
- Predawn leaf water potentiale2
- Setting
- 1-m depth in the rhizospherese2
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sap flux density in branches, leaf transpiration, stomatal conductance and leaf water potentials were measured in 16-year-old Quercus suber L. trees growing in a plantation in southern Portugal”
e2“Predawn leaf water potential reflected soil water potential measured at 1-m depth in the rhizospheres of most trees”
Claim · model-written summary
The lowest predawn leaf water potential of Quercus suber was -1.8 MPa.
- Taxon
- Quercus suberQuercus subere0
- Outcome
- lowest predawn leaf water potentiale3
- Value
- -1.8 MPae3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sap flux density in branches, leaf transpiration, stomatal conductance and leaf water potentials were measured in 16-year-old Quercus suber L. trees growing in a plantation in southern Portugal”
e3“The lowest predawn leaf water potential recorded during this period was -1.8 MPa”
Claim · model-written summary
Mean maximum stomatal conductance of Quercus suber declined from 300 to 50 mmol m(-2) s(-1).
- Taxon
- Quercus suberQuercus subere0
- Outcome
- maximum stomatal conductancee4
- Direction
- declinede4
- Value
- 300 to 50 mmol m(-2) s(-1)e4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sap flux density in branches, leaf transpiration, stomatal conductance and leaf water potentials were measured in 16-year-old Quercus suber L. trees growing in a plantation in southern Portugal”
e4“Mean maximum stomatal conductance declined from 300 to 50 mmol m(-2) s(-1)”
Claim · model-written summary
Transpiration of Quercus suber was reduced from 6 to 2 mmol m(-2) s(-1).
- Taxon
- Quercus suberQuercus subere0
- Outcome
- transpiratione5
- Direction
- reducinge5
- Value
- 6 to 2 mmol m(-2) s(-1)e5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sap flux density in branches, leaf transpiration, stomatal conductance and leaf water potentials were measured in 16-year-old Quercus suber L. trees growing in a plantation in southern Portugal”
e5“reducing transpiration from 6 to 2 mmol m(-2) s(-1)”
Claim · model-written summary
Stomatal conductance of Quercus suber was strongly coupled to changes in soil water content.
- Taxon
- Quercus suberQuercus subere0
- Treatment
- changes in soil water contente6
- Outcome
- stomatal conductancee6
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sap flux density in branches, leaf transpiration, stomatal conductance and leaf water potentials were measured in 16-year-old Quercus suber L. trees growing in a plantation in southern Portugal”
e6“There was a strong coupling between changes in soil water content and stomatal conductance”
Claim · model-written summary
Midday leaf water potentials of Quercus suber did not differ among trees.
- Taxon
- Quercus suberQuercus subere0
- Outcome
- midday leaf water potentialse7
- Direction
- no differencese7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sap flux density in branches, leaf transpiration, stomatal conductance and leaf water potentials were measured in 16-year-old Quercus suber L. trees growing in a plantation in southern Portugal”
e7“there were no differences in midday leaf water potentials”
Claim · model-written summary
Leaf water potential changes in Quercus suber are regulated through stomatal closure, diurnally and seasonally.
- Taxon
- Q. suberQuercus subere1
- Outcome
- changes in leaf water potentiale1
- Qualifier
- stomatal closuree1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sap flux density in branches, leaf transpiration, stomatal conductance and leaf water potentials were measured in 16-year-old Quercus suber L. trees growing in a plantation in southern Portugal”
e1“The strong regulation of changes in leaf water potential in Q. suber both diurnally and seasonally is achieved through stomatal closure”